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J/ApJ/554/202       ROSAT X-ray observations of M81          (Immler+, 2001)

ROSAT X-ray observations of the spiral galaxy M81. Immler S., Wang Q.D. <Astrophys. J. 554, 202 (2001)> =2001ApJ...554..202I
ADC_Keywords: X-ray sources ; Radio sources Keywords: galaxies: individual (M81) - galaxies: general - galaxies: spiral - X-rays: galaxies - X-rays: general - X-rays: ISM Abstract: We present results from the analysis of deep ROSAT HRI and PSPC observations of the spiral galaxy M81. The inferred total (0.5-2keV band) luminosity of M81 is ∼3x1040ergs/s, excluding the contribution from identified interlopers found within the D25 ellipse. The nucleus of the galaxy alone accounts for about 65% of this luminosity. The rest is due to 26 other X-ray sources (contributing ∼10%) and to apparently diffuse emission, which is seen across much of the galactic disk and is particularly bright in the bulge region around the nucleus. Spectral analysis further gives evidence for a soft component, which can be characterized by a two-temperature optically thin plasma with temperature at ∼0.15 and 0.60keV and an absorption of the galactic foreground only. These components, accounting for ∼13% of the X-ray emission from the region, apparently arise in a combination of hot gas and faint discrete sources. We find interesting spatial coincidences of luminous (1037-1040ergs/s) and variable X-ray sources with shock-heated optical nebulae. Three of them are previously classified as supernova remnant candidates. The other one is far off the main body of M81 but is apparently associated with a dense H I concentration produced most likely by the tidal interactions of the galaxy with its companions. These associations suggest that such optical nebulae may be powered by outflows from luminous X-ray binaries, which are comparable to, or more luminous than, Galactic "microquasars." File Summary: File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 98 46 ROSAT HRI M81 source list table4.dat 66 69 ROSAT PSPC M81 source list table5.dat 62 30 ROSAT M81 source identifications table6.dat 72 3 Position Coincidence between X-Ray sources and SNR candidates
See also: IX/28 : ROSAT HRI Pointed Observations (1RXH) (ROSAT Team, 2000) IX/30 : Second ROSAT PSPC Catalog (ROSAT, 2000) IX/31 : The WGACAT version of ROSAT sources (White+ 2000) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 3 A3 --- HNN Source name (where H denotes HRI) (G1) 5- 6 I2 h RAh Right Ascension (J2000) 8- 9 I2 min RAm Right Ascension (J2000) 11- 15 F5.2 s RAs Right Ascension (J2000) 17 A1 --- DE- Sign of the Declination (J2000) 18- 19 I2 deg DEd Declination (J2000) 21- 22 I2 arcmin DEm Declination (J2000) 24- 27 F4.1 arcsec DEs Declination (J2000) 29- 32 F4.1 arcsec R90% The 90% confidence error radius of the source position (1) 34- 39 F6.1 10-4.ct/s CR Net count rate (2) 41- 44 F4.1 10-4.ct/s e_CR Uncertainty in CR (2) 46- 48 A3 --- Com Comment regarding source variability
Note (1): Includes 3.5" systematic error for the attitude solution. Note (2): Corrected for vignetting, exposure and dead-time.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 3 A3 --- PNN Source name (where `P' denotes PSPC) (G1) 5- 6 I2 h RAh Right Ascension (J2000) 8- 9 I2 min RAm Right Ascension (J2000) 11- 14 F4.1 s RAs Right Ascension (J2000) 16 A1 --- DE- Sign of the Declination (J2000) 17- 18 I2 deg DEd Declination (J2000) 20- 21 I2 arcmin DEm Declination (J2000) 23- 24 I2 arcsec DEs Declination (J2000) 26- 30 F5.1 ct/ks CR Net count rate in the 0.5-2keV band 32- 34 F3.1 ct/ks e_CR Uncertainty in CR 36- 40 F5.2 --- HR1 First hardness ratio (1) 42- 45 F4.2 --- e_HR1 Uncertainty in HR1 47- 51 F5.2 --- HR2 Second hardness ratio (2) 53- 56 F4.2 --- e_HR2 Uncertainty in HR2 58- 65 A8 --- Com Further HRI source positional coincidences and variability comments
Note (1): Defined as HR1=(hard-soft)/(hard+soft) where `soft' and `hard' denote source net count rates in the 0.11-0.41keV and 0.52-2.01keV bands, respectively. Note (2): Defined as HR2=(hard2-hard1)/(hard2+hard1) and `hard1' and `hard2' are the split of a hard-band rate into two 0.52-0.90keV and 0.91-2.01keV bands, respectively.
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 3 A3 --- HNN HRI ROSAT name (HNN) (G1) 5- 7 A3 --- PNN PSPC ROSAT Name (PNN) (G1) 9- 12 F4.1 arcsec Offset Offset from the X-ray position 14- 18 F5.2 mag Rmag ? R magnitude 20- 24 F5.2 mag Bmag ? B magnitude 26 A1 --- l_B-R Limit flag on B-R 27- 31 F5.2 mag B-R ? B-R colour index 33- 62 A30 --- Id Identification (1)
Note (1): Identifications: GS: HST Guide Star Catalog v1.1, Cat. I/220 U: USNO A-v2.0 Catalog of Astrometric Standards, Cat. I/252 MF: SNR candidate number from Matonick & Fesen, 1997ApJS..112...49M [MF97] M 81 NN in Simbad X: Einstein X-ray source number from Fabbiano, 1988ApJ...325..544F [F88] X-NN in Simbad Ho IX: Holmberg IX dwarf galaxy.
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
1- 5 A5 --- [MF97] SNR designation (MF NN = [MF97] M 81 NN in Simbad) 7- 8 I2 h RAh Right Ascension (J2000) 10- 11 I2 min RAm Right Ascension (J2000) 13- 16 F4.1 s RAs Right Ascension (J2000) 18 A1 --- DE- Sign of the Declination (J2000) 19- 20 I2 deg DEd Declination (J2000) 22- 23 I2 arcmin DEm Declination (J2000) 25- 28 F4.1 arcsec DEs Declination (J2000) 30- 32 F3.1 arcsec Offset Offset between X-ray and optical positions 34- 40 E7.1 W LHa Hα luminosity 42- 45 F4.2 --- [SII]/Ha Ratio of [SII] to Hα 47- 48 I2 pc Size Size 50- 56 A7 --- Opt Optical shape 58- 60 A3 --- HNN HRI ROSAT source name (G1) 61 A1 --- --- [/] 62- 64 A3 --- PNN PSPC ROSAT source name (G1) 66- 72 E7.1 W LX X-ray luminosity
Global notes: Note (G1): Designations in Simbad: HNN = <[IW2001] HNN> PNN = <[IW2001] PNN>
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 10-Sep-2001
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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